The problem of providing a communications service in a very short time in certain environments where there is still no infrastructure (as usually occurs in new development areas outside large cities), or in places where there already exists such an infrastructure but which is now saturated, has resulted in numerous resources having been dedicated to the definition and design of specific networks that provide a solution for this situation, this solution being preferably based on existing networks or new ones that are easy and quick to install.
Since the introduction of cellular mobile systems, their use has been extended to other purposes than those for which they were originally conceived. One of the most attractive from the point of view outlined above is that known as a "fixed cellular network", which is based on the use of terminals compatible with the cellular network of which it makes use, in a fixed environment. The antenna of the system is usually lodged in a fixed site (normally on roofs) and is usually of the directional type, pointed towards the base station that covers the cell in which it is located.
All this is explained in the U.S. Pat. No. 4,658,096, in which the base stations of a cellular system communicate with fixed cellular terminals that comprise the corresponding interface systems each of which offers a single subscriber line to which may be connected a standard telephone, as well as with the corresponding cellular mobile terminals. In the same document a configuration is also shown in which a communications service is provided for a number of standard telephones, all of the latter being connected to a unit that acts as a concentrator for sharing the communications channels offered by a smaller number of fixed cellular terminals and thereby optimising the existing resources.
The fixed cellular terminals, as indicated in above patent, provide as many subscriber lines as there are cellular transceivers. When a greater number of subscriber lines is needed, some cellular transceivers are grouped.
This kind of fixed cellular service is an alternative available to telecommunications operators who wish to offer their services in determined environments rapidly, and which must desirably be completely transparent for the user in all aspects like, for example, numbering, charging, etc.
On the other hand, this type of fixed cellular terminal does not make use of the features of mobility between cells, roaming for the mobile terminal, etc., consequently the use of cellular service channels does not detract significantly from the potential of the cellular mobile system as such, since the load of "fixed" channels occurs only on one base station, and their maximum number is limited and known.
Nonetheless, optimum economic benefit is not achieved by the prior art because it is necessary to construct a local infrastructure in the subscribers' building in order to distribute the available lines over the set of fixed cellular terminals and have the same number of telephone sets (or terminals of a different type) as fixed cellular terminals in order to cover the communications requirements of the local system.